R-Tech TIG 500 AC/DC, Operating Instructions Manual

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3.5 Aluminium
Is a high quality process widely used for welding
aluminium, particularly in section size up to
about 6mm.The process may be operated with
or without filler.
TIG welding of aluminium can be carried out
using any of the three standard operating
modes, alternating current (AC), direct current
electrode negative (DCEN) and direct current
electrode positive (DCEP).
AC is the most frequently used since with
AC cleaning of the oxide film occurs on the
electrode positive cycle and heating occurs on
the electrode negative cycle.With aluminium
the surface oxide film must be removed to
allow full fusion to take place and AC TIG
does this efficiently, allowing high quality joints
to be made. High purity argon and argonhelium
shielding gas mixtures can be used.
The AC output may be conventional sine wave
or square wave and many electronic power
sources allow the AC waveform to be adjusted,
and also provide facilities for pre- and post- gas
flow and current slope-in and slope-out.
3.6 Balanced Squarewave
The balance on squarewave machines can be
adjusted to achieve the desired results. Greater
amounts of EN create a deeper, narrower
weldbead and better joint penetration.This
helps when welding thick material and promote
faster welding speeds. Greater amounts of EP
removes more oxides from the surface but also
have a shallower penetration.